In one of the crashes, on the northbound side of the freeway between Magnolia and Ontario avenues in the Corona area, 20 people were transported to hospitals, according to California Highway Patrol Officer Travis Monks.

The Corona Fire Department requested all lanes be closed as emergency crews respond, according to the Highway Patrol’s online incident website.

A Fire Department official described the incident as “multi-casualty.”

The bus was en route to Westminster, in Orange County, returning from Pala Casino in Pala, east of Camp Pendleton, according to Monks.

Corona Fire Chief John Media later said 35 adults were on the bus and 22 of them were taken to local hospitals, including several to trauma centers.

After interviews with the driver, Jian Fei Duan, 35, of Baldwin Park, and passengers, investigators concluded the bus was traveling at 65 mph — an unsafe speed for the wet roadways, Monks said in a news release.

The bus was operated by the tour company Sina Coach, which is based in Walnut, according to the CHP.

That crash occurred within minutes of the second incident that left at least one person dead and several others hurt on the 15 Freeway in Fallbrook, about 40 miles to the south.

That collision, on the southbound side south of State Route 76, also involved a tour bus, according to CHP. A SigAlert for that crash was issued at 2:59 p.m., according to the CHP website.

The charter bus, driven by a 56-year-old man from Compton, was en route to the Valley View Casino after leaving the Panorama City area, according to CHP officers at the scene. The driver indicated that his bus company was from the city of Bell.

The driver stated that he was traveling in the no. 4 lane at 55 mph when his bus started to lose control on the roadway, said CHP officer Jim Bettencourt. The driver attempted to correct the now out-of-control bus, but was unsuccessful.

The bus continued to the right shoulder and overturned on its left side, Bettencourt said. Slick roadways in the area due to recent rain may have prevented the bus driver from regaining control of the bus, Bettencourt said.

At least one person was killed. She was identified as 64-year-old woman from Glendale who was partially ejected and became trapped underneath the bus, Bettencourt said.

The 22 injured passengers were taken to Palomar Hospital, Fallbrook Hospital and Tri City Medical Center.

The crashes came as rain and snow hit Southern California amid a cold storm system that prompted the National Weather Service to warn about potentially dangerous road conditions.

No other vehicles were involved in this collision and neither alcohol nor drugs appear to be a factor, Bettencourt said.

The crash remains under investigation.

Correction: An earlier version of this story erroneously reported several people were killed in the Corona incident. It was not immediately clear the extent of the injuries.